The present invention relates to a computational graceful degradation method using priority information in multiple objects case. More particularly, the present invention relates to a method for degrading the amount of computation in different ratio every video object using the priority information if computational power of a decoder does not come up to that necessary for processing encoded multimedia data as decoding the multimedia data encoded by several objects unit, the priority information being determined by an encoder for optimal graceful degradation in terms of relatively visual importance between respective video objects.
Recently, the MPEG (Moving Picture Experts Group) standard, i.e., an international standard of media integration type moving picture compressing technique capable of compressing many informations, have been widely used according to development of multimedia techniques integrating audio, data and video.
MPEG techniques capable of compressing many informations are applied to a communication, broadcasting, home appliances, computer, CD-ROM, etc., to synchronize the audio and video, thus multiplexing the audio and video.
Generally, a bitrate of MPEG bitstream data, which is a system stream mixed with the audio and video signals, is determined according to a kind of channel and memory or display. Such a bitstream data is received to the MPEG decoder and first, decoding of the system stream is executed to obtain audio bitstream informations, video bitstream informations and additional informations mixed into the system stream.
The prior art MPEG decoder decodes MPEG bitstream data to write the decoded results in an external memory. Then, the decoder converts the decoded results into analog signals so that we can hear the audio or see the video.
Generally, since each platform has different computational power, it is necessary to provide the maximum quality of the services which is achievable with the capabilities of each platform. And also, it is mandatory that all decoders can decode all MPEG-4 services but at different levels of quality. It means that a scalability based on computational power is needed. The scalability should enable a graceful degradation of the quality when less than theoretically necessary computational power is available at decoding side.
The conventional computational graceful degradation method has been proposed in MPEG96/0925 by M. Mattavelli et al. to reduce the amount of computation when decoding the encoded multimedia data. The method decreases, in a lump, the amount of computation necessary for decoding without consideration of relative importance between the respective video objects if computational power of the decoder does not come up to that necessary for processing the encoded multimedia data. In the conventional method, however, there exists a problem which does not make full use of the relative importance between the respective video objects.
The conventional method has considered only a single video object (VO) case. A video scene, however, is composed of multiple VOs which can be further decomposed into several video object layers (VOLs) in order to allow scalability. The various degree of visual importance of these VOs and VOLs should be exploited for the simplified decoding in the context of computational graceful degradation.
Accordingly, it is an object of the present invention to provide a method for degrading the amount of computation in different ratio every video object using the priority information if computational power of a decoder does not come up to that necessary for processing encoded multimedia data, the priority information being determined by an encoder for optimal graceful degradation in terms of relatively visual importance between respective video objects.
According to the present invention, there is provided a computational graceful degradation method in an MPEG encoder and decoder system comprising: an encoder including a multimedia object dividing unit for dividing an input multimedia into a plurality of objects according to its content and characteristic, a plurality of object encoding units for encoding the corresponding input multimedia objects from the multimedia object dividing unit, a multiplexer for multiplexing a plurality of encoded multimedia object bitstreams to transmit a multiplexed multimedia object bitstream; and a decoder including a demultiplexer for demultiplexing the multiplexed multimedia object bitstream received from the multiplexer to output a plurality of demultiplexed multimedia object bitstreams, a plurality of object decoding units for decoding the corresponding multimedia object bitstream applied from the demultiplexer, and a multimedia constructing unit for reconstructing the decoded multimedia objects to generate a reconstructed multimedia to user.
The method comprises the steps of determining, in the multiplexer, a priority of the respective objects according to relative importance between the objects before multiplexing the encoded object bitstreams to transmit, considering that the computational graceful degradation will be applied in the decoder, and determining, in the demultiplexer, an amount of computation to be degraded in different ration every video object using the priority information determined according to the respective objects.
The step for determining the amount of degrading computation comprises after demultiplexing the multiplexed object bitstream, analyzing the respective demultiplexed object bitstreams to predict the computational power required to decode the respective demultiplexed object bitstreams, analyzing the computational power of the object decoding units, deciding whether the computational power of the object units exceeds that required to decode the respective demultiplexed object bitstreams or not, and deciding an amount of computation to be degraded every video object using the priority information, if the computational power of the object decoding units does not come up to that required.
According to the above present invention, the multimedia decoding which is more suitable for a characteristic of the respective object can be executed in the same case, by computational graceful degradation in terms of relatively visual importance between the multimedia objects having characteristic different from each other.